1. Field of the Invention
The present invention relates generally to the field of detecting and measuring impacts to the head and resulting neurological impairment. More particularly, it concerns measuring the differential acceleration (including for example, a linear, angular, and/or rotational differential acceleration) of the head in comparison to the body to detect potential traumatic brain injury.
2. Description of Related Art
Traumatic brain injury is caused by head trauma after impact. The rapid acceleration or deceleration of the brain within the cranial vault, or absorption of a shock wave can cause the brain to impact the inside of the skull. These forces can also cause stretching and/or shearing of axonal tracts (tearing of connections between neuronal cells), which can trigger secondary neurodegenerative damage and maladaptive plasticity leading to chronic neurological dysfunction. The physiological effects resulting from these injuries can be detected immediately in some cases, but can also develop slowly over minutes, hours, weeks, months, or even years post-injury. Pathological processes can evolve slowly, making them difficult to detect in stages when interventions are most effective. Mild Traumatic Brain Injuries (mTBI) can result in post-concussion syndrome and impairment in cognitive domains such as memory, processing speed, affect, impulse control, prediction/planning and other executive functions as measured by traditional neuropsychological instruments. Acute physiological changes (e.g. inflammation) following mTBI may also make an individual more susceptible to a subsequent impact due to poor judgment or slower reaction times. These repeated impacts may, in turn, make an individual more susceptible to chronic neurological injury. Therapeutic options may be developed to prevent chronic neurological damage if we can identify reliable quantitative markers (changes in physiological and neurobehavioral responses) associated with mTBI. These quantitative measures could also be used in conjunction with acceleration measurements to identify those types of impacts associated with acute and chronic neurological injury. However, there are currently no devices capable of accurately and objectively tracking subtle changes in neurophysiological status associated with either mTBI or systems that accurately measure angular acceleration of the head correlated with mTBI biomarkers.
There is a critical need to identify a sensitive, rapid, easily obtainable biomarker to serve as an objective indicator of when an athlete or soldier should be withheld from the field and when they can return in order to avoid permanent traumatic brain injury. Repeated concussive and even sub-clinical exposures to head trauma can produce a spectrum of chronic traumatic encephalopathy (CTE), resulting in stress points of damage in the brain, ranging in severity from mild cognitive impairment to severe dementia, disinhibited violent outbursts, motor dysfunction, reduced quality of life and even suicide.
There are currently several wearable accelerometer units available commercially. While each provides an indication of linear acceleration/deceleration, none of the existing devices alone accurately measures differential acceleration of the head relative to the body, which may in fact be a key component in the production of concussion symptoms, as linear measures alone have shown limited correlations with concussion symptoms. It is likely that movement of the head relative to the body is a critical factor in traumatic brain injuries due to the tethering forces of the spine on the brain.